"Good game, but not a good sequel"

[cheesesteak]

Final Fantasy X-2 comes to mind.

Great example. The ATB, job system, and mission-based events were really cool but I didn't think FFX really needed a sequel.

Heh, I'm actually pretty excited to finally play FFX-2. It's probably...5-10 backlog games away, but I'm still excited for it. And now know a little bit more on what to expect.

Metal Gear Solid 4 would be an amazing game if it didn't ruin the story, characters and themes of every MGS game before it.

Metal Gear Rising if only because it's so far removed from what Metal Gear is while still being perfectly fine on its own merits.

Heh, I was actually thinking of the MGS series when posting this. I'd say MGR:R is an exception, since it's a clear spinoff title - it's fine to stray from its parent series themes and sensibilities. But yes, I kept thinking "how does MGS4 hold up as a MGS game?" Great game, but it never stood out to me as a great MGS game. But at the time of the OP, I just couldn't really get a proper hold of my memory.

Breath of the Wild. Great game, sure, but as a Zelda game it was severely underwhelming to me.

An actual excellent example. I should have thought of this. It actually makes me think of other series that shifted genres mid-series. Darksiders III? Went from zeldalike hack-n-slash to soulslike MV hack-n-slash. But I never played Darksiders 3, so I don't really have an insightful opinion.